1. Field of the Invention
This invention relates to an imaging apparatus. This invention particularly relates to an imaging apparatus, which comprises a solid-state detector provided with a layer containing amorphous selenium as a principal constituent.
2. Description of the Related Art
Systems for recording and reading out radiation image information by utilizing solid-state detectors have heretofore been proposed. With the proposed systems for recording and reading out radiation image information, such that a radiation dose delivered to an object during a medical X-ray image recording operation may be kept small, and such that the image quality of an image and its capability of serving as an effective tool in, particularly, the efficient and accurate diagnosis of an illness may be enhanced, a solid-state detector, which is provided with a photo-conductive material sensitive to radiation (such as X-rays), e.g. a selenium plate constituted of amorphous selenium (a-Se), or the like, is employed. The solid-state detector is exposed to radiation for recording (i.e., recording light), such as X-rays, carrying radiation image information, and electric charges carrying the radiation image information are accumulated as latent image charges in a charge accumulating section formed within the solid-state detector. Thereafter, the solid-state detector, on which the radiation image information has been recorded, is scanned with an electromagnetic wave for reading (i.e., reading light), such as a laser beam, and electric currents occurring within the solid-state detector are detected via flat plate-shaped electrodes or stripe-shaped electrodes located on opposite sides of the solid-state detector. In this manner, an electrostatic latent image, which is carried by the latent image charges, i.e. the radiation image information, is read out from the solid-state detector. The systems for recording and reading out radiation image information by utilizing solid-state detectors are described in, for example, U.S. Pat. No. 6,268,614 and U.S. patent application Ser. No. 09/539,412. Also, the applicant proposed a portable type of imaging apparatus, which comprises a compact case housing and a solid-state detector built in the case housing, in, for example, U.S. patent application Ser. No. 09/834,887.
However, the a-Se utilized in the solid-state detector described above has the properties such that the heat resistance is low, and the glass transition temperature (Tg) is as low as approximately 40° C. Therefore, in cases where the temperature within the case housing of the imaging apparatus. rises, and the region within the case housing of the imaging apparatus is kept at a temperature of at least 40° C. for a predetermined period of time, the characteristics of the a-Se change due to crystallization. As a result, there is the risk that an artifact will occur, or the signal-to-noise ratio will become low in a region of the a-Se, in which the characteristics have changed. Accordingly, in cases where the a-Se is employed in one of layers constituting the solid-state detector, which is built in the imaging apparatus, it is necessary that heat occurring within the case housing of the imaging apparatus is dissipated such that the temperature within the case housing does not become higher than the glass transition temperature described above.
Such that the aforesaid temperature rise within a detector may be eliminated, a detector provided with heat dissipation means has been proposed in, for example, Japanese Unexamined Patent Publication No. 2000-153959. In the proposed detector, in order for safety and reliability of the detector to be enhanced, the heat dissipation means is located at a holding section, which is secured to the detector.
In the detector proposed in Japanese Unexamined Patent Publication No. 2000-153959, Se is employed as an example at an X-ray-to-electric charge converting section. However, in Japanese Unexamined Patent Publication No. 2000-153959, nothing is mentioned with respect to the problems inherent to Se (or a-Se), and no specific technique for the elimination of the problems inherent to the a-Se is disclosed.